Abstract

Alzheimer's disease (AD) and semantic dementia (SD) are characterized by different patterns of global and temporal lobe atrophy which can be studied using magnetic resonance imaging (MRI). Manual delineation of regions of interest is time-consuming FreeSurfer is a freely available automated technique which has a facility it) label cortical and subcortical brain regions automatically. As with all automated techniques comparison with existing methods is important. Eight temporal lobe structures in each hemisphere were delineated using FreeSurfer and compared with manual segmentations in 10 control, 10 AD, and 10 SD Subjects. The reproducibility errors for the manual segmentations ranged from 3% to 6% Differences in protocols between the two methods led to differences in absolute volumes with the greatest differences between methods found bilaterally in the hippocampus, entorhinal cortex and fusiform gyrus (p<0.005). However. good correlations between the methods were found for most regions. with the highest correlations shown for the venticles, whole brain and left medial-inferior temporal gyrus (r>0.9), followed by the bilateral amygdala and hippocampus. left superior temporal gyros, right medial-inferior temporal gyrus and left temporal lobe (r>0.8) Overlap ratios differed between methods bilaterally in the amygdala, superior temporal gyrus. temporal lobe, left fusiform gyrus and right parahippocampal gyrus (p:001) Despite differences in protocol and volumes. both methods showed similar atrophy patterns in the patient groups compared with controls, and similar right-left differences, suggesting that both methods accurately distinguish between the three groups.